This invention relates to an optical fiber and lens assembly. More particularly, this invention relates to an optical fiber and lens assembly having a movable lens and a fixed optical fiber.
Optical fiber and lens assemblies are employed for focusing or collimating beams of light in or out of optical fibers, respectively. Such assemblies may be employed singly or in series. In such assemblies, the positioning of the lens(es) and optical fiber(s) depends upon various factors, such as the focal length, wavelength, and intended use of the light. U.S. Pat. Nos. 4,753,510 and 4,889,406, both issued to Sezerman, are directed to adjustable connectors for optically connecting a pair of optical fibers. In the Sezerman patents, an optical fiber is placed contiguous to a lens. The fiber and lens are contained and fixed within a holder which is fixed within a base plate. Such base plate then may be connected to another base plate containing an identical fixed lens and optical fiber assembly. A resilient member is disposed between the base plates. Thus, one fixed fiber and lens assembly may be adjusted with respect to the other fixed fiber and lens assembly. Alternatively, each base plate containing a fixed fiber and lens assembly may be attached to opposite ends of an optical coupling box. A resilient member is disposed between each base plate and the optical coupling box. Each fixed fiber and lens assembly then may be adjusted with respect to the other fixed fiber and lens assembly attached to the opposite end of the optical coupling box. Such attachment is often found to drift out of alignment, and thus requires further adjustment from time to time.
It is an object of the present invention to provide an optical fiber and lens assembly in which the optical fiber is fixed, and the lens is movable with respect to the fiber. This major conceptual difference allows for a more stable device, and thus additional realignment is not required.
In accordance with an aspect of the present invention, there is provided an optical fiber and lens assembly. The assembly comprises a housing, an optical fiber, and means for rendering the optical fiber immobile within the housing. The assembly also includes a lens, and means for moving the lens within the housing.
In one embodiment, the means for rendering the optical fiber immobile within the housing comprises a receptacle means fixed within the housing, and a connector means holding the optical fiber. The connector means fits within the receptacle means to render the optical fiber immobile within the receptacle means and the housing.
The receptacle means may be fixed within the housing by means of cement or adhesive. In a preferred embodiment, in addition to cement or adhesive, the means for rendering the optical fiber immobile within the housing further comprises a clamping means attached to and surrounding the receptacle means. The clamping means holds the receptacle means within the housing.
In one embodiment, the means for moving the lens within the housing comprises a lens holding means containing the lens. The lens holding means is contained within the housing. A reference plate is adjacent the lens holding means. The lens holding means is disposed between the optical fiber and the reference plate. The means for moving the lens within the housing also comprises means for moving the lens holding means along a first axis (sometimes hereinafter referred to as the Z-axis) whereby the lens holding means is moved toward or away from the fixed optical fiber. (Such movement is sometimes hereinafter referred to as movement along the Z-axis, or in the Z-direction.) The means for moving the lens holding means toward or away from the optical fiber comprises at least one screw inserted through the housing and into the reference plate. The means for moving the lens within the housing also comprises means for moving the lens holding means along at least one of a second axis and a third axis (sometimes hereinafter referred to as the X-axis and the Y-axis, respectively) lying in a plane (sometimes hereinafter referred to as the XY plane) disposed at an angle to the first axis, whereby the lens is moved in such plane. (Such movement is sometimes hereinafter referred to as movement along the X-axis and/or the Y-axis, or in the XY plane.) Preferably, the XY plane is nominally perpendicular to the first axis, and the XY plane is nominally parallel to the face of the optical fiber proximal to the lens. The means for moving the lens holding means along the second axis and/or third axis comprises at least one screw inserted through the housing and contacting the lens holding means.
In a preferred embodiment, the means for moving the lens within the housing further comprises a magnet contained within the lens holding means. The magnet is disposed between the lens and the reference plate. The magnet is contiguous with the reference plate, and the reference plate is formed from a magnetic material. The magnetic attraction between the magnet and the reference plate provides for controlled movement of the lens within the housing when the lens is moved along the second axis and/or the third axis (i.e., the X-axis and/or the Y-axis in the XY plane).
In one embodiment, the means for moving the lens holding means along the first axis (i.e., along the Z-axis in the Z-direction) comprises three screws, which are inserted through three openings in the housing to be screwed into three openings in the reference plate. The three screws are spaced circumferentially in the housing and in the reference plate. Each screw is equidistant from the other two screws.
Preferably, the means for moving the lens holding means along the first axis further comprises at least one spring plunger inserted through the housing and contacting the reference plate. More preferably, the means for moving the lens holding means along the first axis further comprises three spring plunger means screwed into three threaded openings in the housing and contacting the reference plate. The three spring plunger means are spaced circumferentially in the housing. Each spring plunger is equidistant from the other two spring plungers.
In operation, the three screws act as "pull screws," whereby the screws pull the reference plate inwardly toward the housing. The spring plungers act as "push screws," whereby the spring plungers push the reference plate away from the interior of the housing. Thus, the screws and the spring plungers exert forces in opposite directions, and thereby act as a "positioning mechanism" for holding the lens and the lens holder in place once the lens holder and lens are moved to a desired position in the housing.
In one embodiment, the means for moving the lens within the housing further comprises at least one leaf spring means attached to the housing and biased against the lens holding means. Such leaf spring means serves to control the movement of the lens holding means within the housing in the XY plane.
In one embodiment, the means for moving the lens holding means along the second axis and/or the third axis comprises at least two screws inserted through the housing and contacting the lens holding means. By moving one or more of the at least two screws, the lens holder and the lens are moved along the second axis and/or the third axis to a desired position in the XY plane against the action of the leaf spring.